Not applicable.
The invention concerns a beam that can be bent for use in a paper or board machine.
In paper or board machines, beams are used, for example, for support of doctor blades, for support of various measurement devices, for support of induction devices, and for support of coating devices. The criteria of dimensioning of beams that support a doctor blade are, as a rule, natural frequency and bending. In the case of steel beams, the principal criterion is, as a rule, natural frequency, in which case the bending rates are, as a rule, rather little. If a support beam is made of a composite material, the decisive criterion will be the bending arising from the load applied by the blade to the beam. One mode of compensating for the bending is to bend the support beam.
In the applicant""s U.S. Pat. No. 3,611,471, one possibility is suggested for bending a doctor device. The frame of the doctor device consists of a box-like frame beam, to which the doctor blade has been attached. In the interior of the box beam, there is a box-like inner beam, whose ends have been attached to the end pieces of the frame beam. To said end pieces, axle journals have also been attached, which axle journals are additionally mounted on support constructions. The mounting of the axle journals permits turning of the doctor device around the longitudinal axis. The axle journals have been coupled with the turning cylinders at the ends of the doctor device, and by means of said turning cylinders the doctor blade can be pressed with the desired force against the face of the roll. Between the vertical walls of the box-like frame of the doctor device and the vertical walls of the box-like inner beam, there are box-like channels extending across the longitudinal direction of the doctor device. In these channels, loading hoses have been fitted, into which hoses a pressure medium can be passed so as to produce the desired loading pressure in said hoses. When pressure medium is passed into one of the loading hoses, it is possible to bend the frame beam to the desired arc form. In this way it is possible to compensate for bending of the middle part of the frame beam. Without this compensation, the doctor blade is pressed against the roll face with a lower force in the middle part of the roll as compared with the edges of the roll. In this prior-art solution, the frame of the doctor device is made of steel.
In the FI Patent Application 965285, a support beam for a coating device is described. The support beam is supported by means of two support points, which are placed, in the longitudinal direction of the beam, on the portion between the centre of the beam and the end of the beam at a distance from the ends of the beam. When the support points are shifted from outside the ends of the beam to between the beam ends and the beam centre, the bending of the beam can be reduced, and the natural frequency of the beam can be raised. Thus, what is concerned here is not active regulation of the bending of the beam, but attempts are made to reduce the bending of the beam by shortening the distance between the support points. Also in this prior-art solution, the support beam is made of steel.
In the applicant""s FI Patent Application 982294, a beam construction of composite material for a paper or board machine is described. The beam is made of a first curved part and of a connected straight part. Doctoring, coating or measurement devices have been mounted on the straight part.
In the applicant""s FI Utility Model Application 980464, a second doctor beam is described, which is made of a composite material and which is placed in connection with a roll or a cylinder in a paper or board machine. The doctor beam comprises at least one such face portion whose shape is curved and complies with the curve form of the adjacent roll mantle.
In the U.S. Pat. No. 5,356,519, a third doctor-blade support beam made of a composite material is described. The beam is provided with an oblong hollow body, which comprises at least two longitudinal convex walls. The length of the radius of the arc defined by the convexity of the walls is longer than the width of the wall, and the walls are interconnected by transition pieces, whose curve radius is shorter than the width of the adjacent oblong wall.
In the beam in accordance with the invention, there is a body made of a composite material. To both ends of the body, end pieces have been fitted, to which end pieces axle journals have again been fitted. The axle journals are supported on the frame constructions of the machine by means of a support construction, which support construction also includes a bending mechanism, by whose means a torque that bends the body of the beam can be applied to the axle journals. When a torque acting in the same direction is applied to the axle journals placed at the ends of the beam, the body of the beam can be bent to the desired arc form. The construction of the beam in accordance with the invention is simple, and its need of servicing is little. The simple construction makes the manufacture of the beam easy and of favourable cost. Also, simple construction facilitates the maintenance of the beam.
A beam of a composite material is of considerably lower weight, as compared with a steel beam, and by means of the bending mechanism mentioned above a bending of the beam can be readily compensated for. By means of the bending mechanism, the beam can be bent to the desired curve form depending on the need in each particular case.
A beam in accordance with the invention can be used, for example, for support of doctor blades, for support of various measurement devices, for support of induction devices, and for support of coating devices.
In the following, the invention will be described with reference to the figures in the accompanying drawings, the invention being, however, not supposed to be confined to the details of said illustrations alone.